Even under questioning, serial rapist Alberto Lugo can’t control the urge.

He’s compulsive, investigators say. Psychotic. Obsessed. But not with the beautiful women he drugs, kidnaps and sexually assaults. Lugo can’t even remember their names.

Instead, Lugo – who faces 50 years behind bars today when he’s sentenced for three attacks – is obsessed with a four-time Golden Glove-winning retired middleweight boxer who grew up with him in the South Bronx.

Even as Lugo sits in an interrogation room facing stern Manhattan prosecutors, he insists he’s not Alberto Lugo.

He says he’s the famous boxer, the famous Bronx Bomber, Alex Ramos – a man Lugo has impersonated continually for almost 20 years, nearly destroying the boxer’s reputation.

“Why don’t you start out by telling me your name,” Assistant District Attorney Martha Bashford told Lugo on Feb. 17, 1999, six days after he slipped a mickey into the beer of an attractive, 27-year-old Atlanta tourist at a Midtown bar, then kidnapped and molested her at the Deauxville Hotel on East 29th Street.

Lugo, 39, gave the prosecutor a bashful smile across the conference table as the taped interrogation got going.

“My name is Alex Ramos,” Lugo told her. “I boxed for a while.”

“Amateur?” the prosecutor asked, straight-faced. “Professional?”

“Both,” the impostor insisted. “Amateur and professional.”

Then, still smiling, he told her that these days, “I just go out and have a good time.”

Lugo the rapist impersonated Ramos the boxer to seduce women – promising them $3,000 a night to work his fights as “ring card girls,” the gorgeous models who strut across the ring holding placards announcing the number of the upcoming round.

He’s been accused of using the ruse to rape at least seven women since the early ’80s.

News of the “Alex Ramos” arrest broke in New York in February 1999, during a week when boxing stars and fans from around the world had flooded into town for the Lennox Lewis-Evander Holyfield fight.

City cops compounded Ramos’ embarrassment by issuing a press release that repeated again and again that the rapist goes by the name “Alex Ramos.”

“Alex Ramos was arrested in 1983 for rape and sodomy,” the release said – referring to a Manhattan attack of which Lugo was convicted in 1985. In that assault, too, Lugo had pretended to be the boxer.

“This has been more damaging to me than any blow inside or outside the boxing ring,” said Ramos, founder of the California-based Retired Boxing Foundation, which helps ex-fighters battle substance abuse, homelessness and the physical ailments that stem from their sport.

His foundation has lost money as a result of the bad publicity, he said.

“I just thank God all of this is going to be behind me,” he said of Lugo’s sentencing. “I just feel sorry for all those poor girls. You have to be crazy to do something like this.